Manufacture of chlorsulphonic acid



Patented July 25, 1944 7 UNITED I STATES PATENT OFFICE I MANUFACTURE oiiiifzitsmrnomc son) I Napoleon Arthur Laury assignor to American This invention relates to a process for the manufacture of chlorsulphonic acid, and more particularly to an improved process for the manufacture ofchlorsulphonic acid from an alkali or alkaline earth metal chloride, sulphur trioxide and sulphuric acid. I

In the past, chlorsulphonic acid has been produced by-reacting sodium chloride with a sulphuric acid solution of sulphur trioxide. The reaction proceeds, in part, as follows:

However, the above designated reactions are unfortunately not the only ones taking place. When salt and oleum are admixed, the sulphuric acid acts rapidly upon the salt to form gaseous hydrogen chloride:

As a result, only about a 38% yield of chlorsulusing sodium chloride for the purposes of illustration:

NaCH-SOz=ClSOzONa Rockvilie Centre, N. Y.,

Cyanamid Company, New York. N. Y., a. corporation of Maine No Drawing. Application June 15, 1942, Serial No. 447,149

6 Claims. (01. 23-139) a contact sulphuric acid plant. Amore concentrated oleum must be prepared by distillation and 100 parts of sodium chlorsulphonate containing it is therefore an important advantage of the present process that comparatively dilute oleum 57.7% $0: and 40.9% NaCl (prepared by' agitating dried commercial sodium chloride ground to about 200 mesh in a vessel and passing a current of sulphur trioxide over it) and 125 parts of oleum containing free $03 are fed continuously-into an oil-heated cast iron retort which is connected by means of a gas flue in its cover to a condenser. The charge is distilled at a temperature between about 146 and 153 C. and 77 parts ofcrude distillate are obtained. This coralthough it should be understood that applicant does not intend that his invention be limited by the theory therein set forth.

If there is no free sulphur trioxide present in the second step of the process, the sodium pyrosulphate, which is produced at this stage instead of neutral sodium sulphate, is formed at the expense of the chlorsulphonic acid yield. I have therefore found it desirable to use sulphuric acid which contains a quantity'ot free sulphur trioxidein order that improved yields of the chlorsulphonic acid be obtained. It is not necessary that the oleum contain a high content of free $03 nor would the use of a concentrated oleum possess any advantage in a commercial process. Excellent results may be obtained with oleum containing up to 40% free sulphur trioxide such as ess.

is readily obtainable from theconverter gases of 66 responds to a 91.5% yield of chlorsulphonic acid, based on the sodium chloride used; If the product contains dissolved sulphur trioxide, it may be removed by distillation with a small quantity of sodium chloride. I During the reaction the pyrosulphate by-product accumulates in the retort audit is maintained at an approximately constant level by pumping some out once during each shift. A depth or 4 or 5 feet in .the retort serves as a good working medium and heat reservoir. The temperature of the pool or acid sulphate in the retort must be high enough to keep it fluid'aud easily pumped, but it is best not to let it exceed 250' C.

, It should be understood that the invention is not limited to the use ofsodium chloride and any other-alkali or alkaline earth metal chloride such as potassium chloride, calcium chloride, and the like, may be substituted therefor. Moreover, the processmay also be carried out as a batch proc- The sulphur trioxide used in the preparation 01' sodium chlorsulphonate need not be very concentrated or of particularly high purity. The gas mixture issuing from the converter of a contact sulphuric acid plant may advantageously be utilized.

- containing up to about 40% free sulphur trioxide to produce and distill ofl chlorsulphonic acid.

2. A process for manufacturing chlorsulphonic acid which comprises first reacting gaseous sulphur trioxide with a member of the group consisting of alkali and alkaline earth metal chlorides to form thecorresponding chlorsulphonate and then heating the chlorsulphonate with fuming sulphuric acid containing up to about 40%- free sulphur trioxide to produce and distill oi! chlorsulphonic. acid,

3. A process for manufacturing chlorsulphonicacid which comprises first reacting gaseous sulphur trioxide with an alkali metal chloride to form the corresponding chlorsulphonate and 1 then heating the chlorsulphonate with fuming sulphuric acid containing up to about 40% free sulphur trioxide to produce and distill oi! chlorsulphonic acid.

4. A process for manufact ing chlorsulphonicacid which comprises first reacting sodium chloride with the sulphur trioxide containing'gas mixture which issues from the converter of a contact sulphuric acid plant to form sodium chlorsulphonate, and then heating the sodium chlorsulphonate with fuming sulphuric acid containing up to about 40% free sulphuktrioxlde to produce and distill ofl chlorsulphonic acid.

5. A process for manufacturing chlorsulphonic acid which comprises first reacting gaseous sulphur trioxide with sodium chloride to form sodium chlorsulphonate, and then heating the sodium chlorsulphonate with an excess of fumin sulphuric acid containing up to about 40% free sulphur trioxlde at a temperature or about 146 C. to about 153 C to produce and distill or! chlorsulphonic acid.

- 6. A process for manufacturing chlorsulphonic acid which comprises first reacting gaseous sulphur trioxide with sodium chloride to form sodium chlorsulphonateythen heating the sodium chlorsulphonate with fuming sulphuric acidcontaining up to about 40% free sulphur trioxide to produce chlorsulphonic acid, and continuously distilling the chlorsulphonic'acid from a pool of molten sodium pyrosulphate.

NAPOLEON A 'mUR LAURY. 

